1. Thermo-economic modelling and optimization of fuel cell systems Francesca Palazzi, Julien Godat, Dr François Marechal Laboratory for Industrial Energy Systems LENI ISE-STI-EPFL Swiss Federal Institute of Technology - Lausanne mailto:francois.marechal@epfl.ch STI ISE LENI LENI

2. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 2 Presentation Plan Thermo-ecomomic modelling and optimization of fuel cell systems Methodology Modelling: integrated PEM system Results Discussion

3. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 3 Thermo-economic optimization Energy integration Configuration options Project goals Optimal design of FC systems where the configuration is unknown a priori FC-system model

4. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 4 Chemical process modelling tool Thermodynamic calculations Block system equation solver Modular graphical interface VALI-BELSIM, Belgium www.belsim.com Methodology Process flow model VALI

5. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 5 Process integration techniques Optimal heat exchange system model Additional hot and cold energy resources optimization Integrated system energy balance Under development at LENI leniwww.epfl.ch Energy integration EASY Methodology Process flow model VALI

6. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 6 Multi-Objective Optimizer (Mixed Integer Non-Linear Programming) Based on advanced evolutionary algorithms Applicable to complex problems with discontinuities Robust and allow global optimization (multi-modal problems) Developed at LENI leniwww.epfl.ch Methodology Process flow model VALI Energy integration EASY Optimisation MOO

7. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 7 Methodology Process flow model VALI Energy integration EASY Optimisation MOO PerformancesDecision variables State variables Heat exchange requirements State variables Equipment rating and costing

8. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 8 Process flow model VALI

9. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 9 Energy flow model PEM system modelling (VALI): define the process steps Fuel processing Fuel Cell Post combustion Heat exchange requirements To energy integration (EASY)

10. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 10 Energy flow model of subsystems Fuel processing Fuel Cell Post combustion Fuel processing Post processing Cleaning

11. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 11 Subsystems superstructure Fuel processing Post processing Cleaning Process Alternatives (energy flow level (VALI))

12. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 12 Energy flow model Utility

13. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 13 Energy integration EASY

14. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 14 Energy integration Pinch technology, composite curves H T H T C p =a C p =c C p =b T2T2 T1T1 T3T3 T4T4 T5T5 Cold streams (Tin < Tou) = heat required Hot streams (Tin > Tou) = heat available Minimum of Energy Required Minimum of Energy to Evacuate Hot Utility: supplies energy to the system Cold Utility: removes energy from the system Hot composite curve Cold composite curve Possible heat recovery by heat exchange

15. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 15 Utility system optimization Selection of the best utility system Combined heat and power Resolution by optimization inside EASY Additional methane flow rate Air excess flow rate Hot Utility = Additional Firing Cold Utility = Air Excess

16. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 16 Methodology Optimisation MOO

17. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 17 MOO: multi-objective optimizer Evolutionnary algorithm Multi-objective optimization Mixed Integer Non-Linear Programming Clustering techniques Identify global and local optima

18. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 18 Objectives: thermo-economic Two objectives: Maximum Efficiency Minimum Specific Cost

19. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 19 Methodology Equipment rating and costing

20. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 20 Objectives computation Efficiency: Methane lower heating value [kJ/kmol] Methane entering the system [kmol/s] Fuel Cell power [kW] Resulting power from turbines and compressors [kW] Electrical power cost of the oxygen production [kW] Power balance on the system [kW]

21. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 21 Objectives computation Specific Cost: Post combustion unit investment cost Fuel cell investment cost Fuel processing unit investment cost Methodology based on scaling from a reference case: R. Turton, Analysis, Synthesis and Design of chemical processes, Prentice Hall, NJ, 1998 Empirical formulas and reference cases: C.E. Thomas, Cost Analysis of Stationary Fuel Cell Systems including Hydrogen Co-generation, Directed Technologies, 1999 www.directedtechnologies.com. www.directedtechnologies.com State variables Units sizing Cost computation

22. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 22 Decision variables Fixed methane flow rate Selection T FP Steam / carbon Air enrichment Fuel Utilization Post combustion pressure Oxygen to carbon

23. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 23 Results: Pareto curve

24. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 24 Pareto analysis ATR SMR

25. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 25 Pareto analysis Steam to carbon ratio of the optimal points

26. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 26 Pareto analysis Fuel processing temperature of the optimal points

27. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 27 Pareto analysis Post combustion pressure of the optimal points

28. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 28 Pareto analysis Fuel utilization of the optimal points

29. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 29 Results: Cost analysis Specific cost by equipment [$/kW] 1 2 3 10 1 2 3 4 5 6 7 8 9 10 4 5 67 8 9 1200 800 400

30. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 30 Two level optimization: –Energy Integration –Thermo-economic Optimization Complete tool for help to system design Process alternatives can be easily implemented in the existing superstructure (Fuel processing, SOFC, …) Interesting regions of the model are identified for further investigation Summary Complete tool for help to system design

31. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 31 Aknowledgment The authors thank the Swiss Federal Office of Enegy for the financial support of the present project

32. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 32 I´ll be glad to answer your Qestions !

33. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 33 Pareto analysis

34. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 34 Pareto analysis

35. F.Palazzi – Laboratory for Industrial Energy Systems - LENI ISE-STI-EPFL – March 2004 35 Power analysis Fraction of electrical power produced by each subsystem